1. Field of the Invention
The present invention relates to a heating device, which includes a substrate having a heating surface and a cylindrical member.
2. Description of the Related Art
There are semiconductor manufacturing apparatuses that include a ceramic heater for heating a wafer. The ceramic heater includes a plate having a heating surface and a cylindrical member supporting the plate. For example, a ceramic heater having multiple heating elements in the plate is disclosed (e.g., Japanese Patent Application Laid-open No. 2001-102157, p. 3–4, FIG. 1). Furthermore, a ceramic heater having the specified difference in coefficient of thermal expansion between the plate and the cylindrical member is disclosed (e.g., Japanese Patent Application Laid-open No. 2003-309049, p. 3, FIG. 1).
However, conventional ceramic heaters allow heat of the heating surface to leave via the cylindrical member joined to the central part of the plate, thereby lowering the temperature only in the central part of the heating surface. When a temperature difference occurs in the heating surface as such, there are concerns for generation of cracks and deformation in the central part of the heating surface. Therefore, there is concern that the useful life will be shortened.
Furthermore, in the case where the plate and the cylindrical member are joined and integrated, when the plate and the cylindrical member are made of different materials differing in thermal conductivity as described in Japanese Patent Application Laid-open 2003-309049, there are concerns for breakage and deformation at the junction of the plate and the cylindrical member due to difference in coefficient of thermal expansion therebetween. Therefore, there is concern that the useful life will be shortened.